Recently, a digital radiography (DR) that uses an X-ray image detection apparatus such as a flat panel detector (FPD) for converting X-rays into digital data has been practically used. The X-ray image detection apparatus has been rapidly distributed since it has a merit in that an image may be immediately confirmed, as compared to a conventional computed radiography (CR) method that uses an imaging plate.
As the X-ray image detection apparatus, various types have been proposed. For example, there is an indirect conversion type which converts X-rays into visible light using a scintillator such as CsI:Tl, GOS(Gd2O2S:Tb) first, and converts the converted light into electric charges which are accumulated in a semiconductor layer. The indirect inversion type X-ray image detection apparatus includes a scintillator and a photodetector having a semiconductor layer.
In such an X-ray image detection apparatus, for example, in a case of being used in a living body, it is preferable to lower the X-ray irradiation dose, and a scintillator with a high luminescence amount and an excellent sensitivity is required. Thus, in order to increase the luminescence amount in the vicinity of the photodetector, there is proposed an X-ray image detection apparatus configured such that a scintillator such as CsI is deposited on a glass substrate of the photodetector and X-rays are irradiated toward scintillator from the photodetector side (see, e.g., Patent Literature 1 and Patent Literature 2).
Here, in theory, as the thickness of the crystal phase of the scintillator is increased, the sensitivity is improved. However, in practice, when the thickness of the crystal phase is increased beyond a limit, there is a problem in that light may be attenuated or disused when passing the scintillator and thus, sufficient sensitivity may not be obtained or blurring of an image may occur. For this reason, an aggregate of columnar crystals that guide emitted light is used (see, e.g., Patent Literature 3). Since the light is guided in the thickness direction of the panel of the scintillator by such columnar crystals and incident on the light director, the sharpness of a detection image is improved.
Here, an X-ray image detection apparatus of Patent Literature 3 is provided with a sensor board including a photoelectric conversion element, a phosphor underlayer having a surface disposed on the sensor board and subjected to an atmospheric pressure plasma processing, and a phosphor layer (scintillator) including columnar crystals formed on the phosphor underlayer in contact with the phosphor underlayer. Through the atmospheric pressure plasma processing to the underlayer, the adhesion between the underlayer and the phosphor layer is improved.